If you want to know what the "emerging church" is (and have and affinity for computer games or science fiction), watch this video:
Spore is to video games what the "emerging church" is to Christianity. It's church where you create the content; where there are no invisible, arbitrary boundaries, and where you tell the story instead of playing the role you're given. The analogies are virtually endless. (Seriously, someone show me where the analogy breaks down. Because I'm sure it must, but am too blown away by this video to figure it out right now.)
The real kicker, though, is that even though Spore is all about making your own story, it still relies on a metanarative, namely evolution, to define the parameters and goals of the game. A truly openended game would be not only boring but unplayable. I think that's because human beings always seek to integrate their story into one that's bigger than their own, and it's the grandest stories that give us the most freedom and fun.
And it's on this point that the "emerging church" has one over on the secular-postmodern worldview. After all, what bigger story is there than the one about the God of the universe trying to win back the hearts of his creatures? I guess you could try to write a hack that would let you play that one as the final level of Spore; or you could just get together with some other believers, use the Bible to define your parameters and goals, and see what emerges.